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Original question:

ADS124S08: ADS124S08

ADS124S08: calibration commands and programming all channels

Ponraj Tamil
Prodigy 170 points
Part Number: ADS124S08

Request you to help us in the following queries:

Firstly thank you very much for the support as we could able to program the ic and get data from a single channel(AIN0,AIN1 sensor connected).

question1:I AM PROGRAMMING THE IC from FPGA.

configuration:

1.Continous conversion mode

2.800 sps

3.PGA 32 GAIN

4.LOW LATENCY FILTER

5.Delay ...>11*tmod

how to program the ic for getting the data from remaining 5 channels as we are using differential inputs. can you help us in flow for acquiring the data for remaining  5 channels.

For acquiring the single channel data i am using following flow:

1.write the data to configuration registers. I am using first five registers. while writing to registers sart/sync is high

2.making start/sync pin low  ,waiting for 24 t clk cycles

3..start/sync high,      waiting for 28 t clk cycles

4.start/sync low,  checking for DRDY to be low

6.data acquisition.

7.going back to 1.

Question2:

a)when to send the calibration commands. Is there any particular sequence to send the calibration commands.?

b)how to send the calibration commands for all channels?

  • 0
    TI__Guru** 112635 points

    Hi Ponraj,

    When using the mux you would follow the same flow as you have it now, but for step 1 you would change configuration to the desired in put channels.  If only the mux channels change within the loop then the loop would appear like the following:

    1. Write the overall device configuration and set the channel count to 0
    2. Set the proper mux settings for desired channel (this is a configuration write to register 0x02 with the desired input channels selected for AINP and AINN)
    3. making start/sync pin low  ,waiting for 24 t clk cycles
    4. start/sync high,      waiting for 28 t clk cycles
    5. start/sync low,  checking for DRDY to be low
    6. data acquisition.
    7. Increment channel counter
    8. If channel count is greater than 6, channel is equal to 0 (six conversions now complete, so start with the first channel again)
    9. going back to 2

    Regarding calibration, this is often unnecessary.  The ADS124S08 is trimmed to meet specifications for all gains.  The only other calibration would be the offset calibration to remove the internal offset of the ADC.  I would recommend just issuing the SFOCAL command once between steps 1 and 2 if you desire.  Here you would issue the command, wait for DRDY to go low to signal the end of the calibration cycle, then continue on from there with step 2.

    Best regards,

    Bob B